Bulletin of the Sea Fisheries Institute 2 (153) 2001 - CEEMaR

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8 IRENA BORZÊCKA various age groups and calendar years that fish entered the river or that the summer sea trout was considerably larger than the winter sea trout. The Table 1 also presents data concerning the sizes of first year growth in the sea in 1962 and 1963. It was greater among winter sea trout than among summer sea trout, and the differences calculated with the t test were highly significant. The dependence between fish body mass and length for winter sea trout females aged 2.1 + , that attained their first annual growth increment in the sea in 1962 and 1963, is described as follows: W = 0.00004 · L 2.707 . A similar function was determined for summer sea trout females aged 2.2 + from the same years of growth: W = 0.00001 · L 2.975 . Exponent b, which describes the rate of body mass growth as fish length increases was slightly lower for winter sea trout than for summer sea trout (Fig. 3). weight [kg] 8 7 winter sea trout 6 5 4 3 2 W = 0,00004iL 2,707 1 40 50 60 70 80 90 100 length [cm] weight [kg] 9 8 summer sea trout 7 6 5 4 3 2 W = 0,00001iL 2,975 1 40 50 60 70 80 90 100 length [cm] Fig. 3. Function describing the relation between mass and length of summer and winter sea trout in the Vistula River
Growth of Vistula sea trout (Salmo trutta m. trutta L.) ... 9 Next, the derived functions were used with the experimental length data for specimens from both the summer and winter stocks to determine the mass. The differences between the average masses estimated by either one or the other function were significant (t =12.2, df. = 218). The Fulton condition K coefficients were similar in both stocks and their average values did not vary significantly. In the case of younger fish, which had accomplished their first growth increment in the sea in 1962 and 1963, the average Fulton coefficients were as follows: for winter females 1.28 ± 0.12 and 1.30 ± 0.15; for summer females 1.30 ± 0.13 and 1.26 ± 0.15. In the case of older fish, the average Fulton coefficients were 1.27 ±0.14 and 1.32 ±0.11 for the winter stock and 1.32 ± 0.19 and 1.26 ± 0.12 for the summer stock. The detailed documentation of all results is given in Table 2. Table 3 presents the average lengths of Vistula sea trout females of a particular age in the sea and the average lengths of the same-aged females originated from other rivers in Poland. The comparison has been favorable both to summer and winter sea trout from the Vistula River. This confirms the exceptional physical qualities of the Vistula sea trout. DISCUSSION The rate of fish growth is dependent on a number of factors, both internal, such as sex, genetic predisposition, position in the stock, fish age, and external, like specimen density, food abundance, water temperature, oxygen content in the water, etc. Sea trout, a diadromous fish, is affected by both freshwater and seawater environmental conditions which can vary annually causing changes in fish growth rates. Sych (1967a) proved that average sea trout body growth increments in the Vistula River vary significantly; it follows that average fish sizes in subsequent years vary as well. The data presented in this work reveals the differences between the average mass and length of both winter and summer sea trout which underwent their first two growth increments in the sea in 1962 and 1963 as well as in 1963 and 1964. It was confirmed that the growth rate of winter sea trout is better than that of summer sea trout. The investigations were carried out using growth measurements after the fish had spent their first season in the sea, since sea trout size is best characterized by the magnitude of body increment in that season (Sych 1967a). The average mass and length of the summer sea trout at the moment they entered the river were higher or the same size as the winter trout. This means that the lower growth rate of summer sea trout in the Vistula River is compensated by their staying in the sea feeding grounds six months longer, which resulted in the spring-summer growth increment just before the migration. The value of the b exponent in the function, which describes the dependence of fish body length and mass in both stocks, was approaching 3, although it was slightly lower in the winter stock. This may indicate the better condition of the summer stock specimens. According to Wawrzyniak’s suggestions (1998), the exponent of this function is a good indicator of fish condition. However, the values of the traditional Fulton coefficient were comparable for both stocks of sea trout. It must be kept in mind though, that the high condition coefficient for winter sea trout reflects a concentration of matter and energy in the fatty tissue before the yearlong migration, whereas for summer sea trout both matter and energy have already been moved to a highly developed reproductive system (Pi¹tek 1961).
Page 1 and 2: ISSN 1429-2335 Bulletin of the Sea
Page 3 and 4: BULLETIN OF THE SEA FISHERIES INSTI
Page 5 and 6: Growth of Vistula sea trout (Salmo
Page 7: Growth of Vistula sea trout (Salmo
Page 11 and 12: Growth of Vistula sea trout (Salmo
Page 13 and 14: BULLETIN O THE SEA ISHERIES INSTITU
Page 15 and 16: Larval scombrids in the northern Ca
Page 31 and 32: 32 S£AWOMIRA GROMISZ AND ZBIGNIEW
Page 35 and 36: Table 1. Taxa which comprised the l
Page 51 and 52: BULLETIN OF THE SEA FISHERIES INSTI
Page 53 and 54: Energy budget in early stages of sm
Page 59 and 60:
Energy budget in early stages of sm
Page 61 and 62:
64 KATARZYNA HORBOWA In the Vistula
Page 63 and 64:
Table 3. Frequency of occurrence (%
Page 65 and 66:
68 KATARZYNA HORBOWA Bryliñska, M.
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WSKAZÓWKI DLA AUTORÓW INFORMACJE
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Bulletin of the Sea Fisheries Institute 2 (153) 2001 - CEEMaR

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